scholarly journals Discarded gems: Thermoelectric performance of materials with band gap emerging at the hybrid-functional level

2021 ◽  
Vol 119 (8) ◽  
pp. 081902
Author(s):  
Kristian Berland ◽  
Ole Martin Løvvik ◽  
Rasmus Tranås
Keyword(s):  
Band Gap ◽  
Thermoelectric Performance ◽  
Hybrid Functional ◽  
Functional Level

Tuning band gap and optical properties of SnX2 nanosheets: Hybrid functional studies

2016 ◽  
Vol 30 (10) ◽  
pp. 1650120 ◽  
Author(s):  
P. Guo ◽  
Y. W. Luo ◽  
Y. Jia
Keyword(s):  
Optical Properties ◽  
Optical Absorption ◽  
Band Gap ◽  
Electronic Structures ◽  
Threshold Values ◽  
Hybrid Functional ◽  
Functional Studies ◽  
Quantum Size ◽  
Light Activity ◽  
Optical Applications

Based on hybrid functional calculations, the electronic structures and optical properties are investigated in the monolayer and bilayer tin dichalcogenides SnX2 (X = S and Se) nanosheets. Numerical results show that quantum size effects are obvious on the electronic structures and optical absorption in the SnS2 and SnSe2 nanosheets. The band gap values increase when the nanosheets layer numbers decrease. Moreover, for SnSe2 nanosheet, the optical absorption coefficients are high and its threshold values lie in the visible light activity range. These results are interesting and indicate that SnS2 and SnSe2 nanosheets may serve as the promising candidates for visible optical applications.

Electronic structures and optical properties of cuprous oxide and hydroxide

2014 ◽  
Vol 1675 ◽  
pp. 185-190
Author(s):  
Yunguo Li ◽  
Cláudio M. Lousada ◽  
Pavel A. Korzhavyi
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
Cuprous Oxide ◽  
Density Functional ◽  
Spent Nuclear Fuel ◽  
Energy Levels ◽  
Chemical Properties ◽  
Density Functional Theory Calculations ◽  
Hybrid Functional ◽  
Indirect Band Gap

ABSTRACTThe broad range of applications of copper, including areas such as electronics, fuel cells, and spent nuclear fuel disposal, require accurate description of the physical and chemical properties of copper compounds. Within some of these applications, cuprous hydroxide is a compound whose relevance has been recently discovered. Its existence in the solid-state form was recently reported. Experimental determination of its physical-chemical properties is challenging due to its instability and poop crystallinity. Within the framework of density functional theory calculations (DFT), we investigated the nature of bonding, electronic spectra, and optical properties of the cuprous oxide and cuprous hydroxide. It is found that the hybrid functional PBE0 can accurately describe the electronic structure and optical properties of these two copper(I) compounds. The calculated properties of cuprous oxide are in good agreement with the experimental data and other theoretical results. The structure of cuprous hydroxide can be deduced from that of cuprous oxide by substituting half Cu+ in Cu2O lattice with protons. Compared to Cu2O, the presence of hydrogen in CuOH has little effect on the ionic nature of Cu–O bonding, but lowers the energy levels of the occupied states. Thus, CuOH is calculated to have a wider indirect band gap of 2.73 eV compared with the Cu2O band gap of 2.17 eV.

scholarly journals First Principles Study on Electronic and Optical Properties of Quinary Copper-based Sulfides and Selenides Cu2HgGe(S1-xSex)4

2021 ◽  
Vol 37 (1) ◽  
Author(s):  
Pham Dinh Khang ◽  
Vo Duy Dat ◽  
Dang Phuc Toan ◽  
Vu Van Tuan
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
Density Functional ◽  
Hybrid Functional ◽  
Electron Hole ◽  
Functional Theory ◽  
Electronic And Optical Properties ◽  
Pair Separation ◽  
Electron Hole Pair ◽  
Band Transition

Electronic and optical properties of Cu2HgGe(S1-xSex)4 compounds (x = 0, 0.25, 0.5, 0.75, and 1) were revealed by density functional theory (DFT), in which the Heyd-Scuseria-Ernzerhof hybrid functional was used. Dependence of band gap on the Se constituent in Cu2HgGe(S1-xSex)4 was reported. The substitution of Se element basically cause a slightly lattice expansion and minor change of the band gap. Meanwhile, the overlap of Cu and S/Se states becomes more dense leading to better electron/hole pair separation and inter-band transition of photo-excited electrons. The Cu2HgGe(S0.75Se0.25)4 compound was predicted to be very promising absorber due to the low band gap, high absorption rate, and low reflectivity in the incoming light energy range from 0 eV to 2 eV.    

Strong Structure Band Gap Relation in Semiconductors: Implications for Computational Band Gap Prediction

2014 ◽  
Vol 1704 ◽  
Author(s):  
David H. Foster ◽  
Guenter Schneider
Keyword(s):  
Band Gap ◽  
Structure Prediction ◽  
Structural Parameters ◽  
Lattice Relaxation ◽  
Valence Band Maximum ◽  
Hybrid Functional ◽  
Relaxation Methods ◽  
Copper Chalcogenide ◽  
The Mean ◽  
Better Than

ABSTRACTStructure prediction for novel materials requires computationally inexpensive lattice relaxation methods. Prediction of the band gap and excited state properties depends on the accuracy of the relaxations and the sensitivity of the band edges to structural parameters. We examine the relaxation performance of common relaxation methods for several members of the type IB3-V-VI4 copper chalcogenide semiconductors, which have become of recent interest for potential photovoltaic and thermoelectric applications. These materials are members of a larger family of materials, composed of type IB and type VI elements and additional elements acting as cations, which contains structures as complex as Cu12Sb4S13 (tetrahedrite) and may benefit from materials prediction studies. Examining Cu3PS4, Cu3PSe4, Cu3AsS4, and Cu3AsSe4, we find that relaxation induced structural errors cause subsequently calculated band gap values Eg to deviate by as much as 0.6 eV from values obtained using experimentally determined structures. Using the HSE06 hybrid functional we find that the complex V/VI* anti-bonding character of the conduction band minimum creates a band gap sensitivity of order 10 eV/Å to the mean V-VI distance 〈V-VI〉. A weaker correlation between Eg and 〈IB-VI〉 exists due to the Cu-d/Ch-p* character of the valence band maximum (Ch = S, Se). Type IB-III-VI2 materials are known to have similar properties and we include CuInSe2, CuAlS2, and CuAlSe2. Regarding structural relaxation accuracy, we find that GGA+U and meta-GGA functional MS2 typically perform better than GGA (PBE) or PBEsol, but not as well as the much more expensive HSE functional.

Enhanced thermoelectric performance of InTe through Pb doping

2021 ◽  
Author(s):  
Shantanu Misra ◽  
Adèle Léon ◽  
Petr Levinsky ◽  
Jiří Hejtmánek ◽  
Bertrand Lenoir ◽  
...  
Keyword(s):  
Energy Conversion ◽  
Band Gap ◽  
Narrow Band ◽  
Thermoelectric Performance ◽  
Chalcogenide Semiconductors ◽  
Type Semiconductor ◽  
P Type ◽  
Pb Doping

Chalcogenide semiconductors continue to be of prime interest for designing novel efficient materials for energy-conversion applications. Among them, the narrow-band-gap p-type semiconductor InTe exhibits high thermoelectric performance that mostly stems...

Electronic and optical properties of CsPb2Br5: A first-principles study

2019 ◽  
Vol 33 (22) ◽  
pp. 1950266 ◽  
Author(s):  
Mingge Jin ◽  
Zhibing Li ◽  
Feng Huang ◽  
Weiliang Wang
Keyword(s):  
Optical Properties ◽  
Optical Absorption ◽  
Visible Light ◽  
Band Gap ◽  
First Principles ◽  
First Principles Calculations ◽  
Hybrid Functional ◽  
Electronic And Optical Properties ◽  
Optical Absorbance ◽  
Indirect Band Gap

There are conflicting understandings of the electronic and optical properties of CsPb2Br5. We investigated the electronic and optical properties of CsPb2Br5 with first-principles calculations. It is confirmed that CsPb2Br5 is a semiconductor with an indirect band gap of 3.08 eV at GGA/PBE level and 3.72 eV at the HSE06 hybrid functional level. The PBE results demonstrate that the inclusion of SOC slightly reduces the band gap. We calculate the optical absorbance/emission spectrum of CsPb2Br5. It is found the optical absorption edges locate at 360–380 nm, shorter than the wavelength of visible light. Our results support the experimental results of Li et al. [Chem. Commun. 52 (2016) 11296] and Zhang et al. [J. Mater. Chem. C 6 (2018) 446].

Hybrid functional calculations on the band gap bowing parameters of InxGa1−xN

2016 ◽  
Vol 37 (4) ◽  
pp. 042001 ◽  
Author(s):  
Mei Lin ◽  
Yixu Xu ◽  
Jianhua Zhang ◽  
Shunqing Wu ◽  
Zizhong Zhu
Keyword(s):  
Band Gap ◽  
Hybrid Functional

Tuning to the band gap by complex defects engineering: insights from hybrid functional calculations in CuInS2

2017 ◽  
Vol 51 (2) ◽  
pp. 025105 ◽  
Author(s):  
Pei Yang ◽  
Li-Jie Shi ◽  
Jian-Min Zhang ◽  
Gui-Bin Liu ◽  
Shengyuan A Yang ◽  
...  
Keyword(s):  
Band Gap ◽  
Hybrid Functional
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